My app was taking 5 seconds to generate an image involving about a million calls to Imager->setpixel and this felt way too slow. NYTProf revealed the cause to be expensive sanity checking in Imager.pm at lines 3456 and 3465. Commenting those lines gets me down to 3 seconds and this now feels much less slow: 
sub setpixel {
  my ($self, %opts) = @_;

#  $self->_valid_image("setpixel") or return;

  my $color = $opts{color};
  unless (defined $color) {
    $color = $self->{fg};
    defined $color or $color = NC(255, 255, 255);
  }

#  unless (ref $color && UNIVERSAL::isa($color, "Imager::Color")) {
#    unless ($color = _color($color, 'setpixel')) {
#      $self->_set_error("setpixel: " . Imager->errstr);
#      return;
#    }
#  }

  unless (exists $opts{'x'} && exists $opts{'y'}) {
    $self->_set_error('setpixel: missing x or y parameter');
    return;
  }
...
}

sub _valid_image {
  my ($self, $method) = @_;
 
  ref $self
    or return Imager->_set_error("$method needs an image object");
 
  $self->{IMG} && Scalar::Util::blessed($self->{IMG}) and return 1;
 
  my $msg = $self->{IMG} ? "images do not cross threads" : "empty inpu
+t image";
  $msg = "$method: $msg" if $method;
  $self->_set_error($msg);
 
  return;
}

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Should the next version of Imager have an option to disable global sanity so it can operate almost twice the usual speed?

In reply to Double the speed of Imager->setpixel by Anonymous Monk

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